1. Field of the Invention
This invention relates to a driving technique for a plasma display panel, and more particularly to a method of driving a plasma display panel and an apparatus thereof that is capable of preventing an abnormal discharge generated at the upper and lower edges of an effective display area of the plasma display panel.
2. Description of the Related Art
Generally, a plasma display panel (PDP) radiates a phosphor using an ultraviolet with a wavelength of 147 nm generated upon discharge of an inactive mixture gas such as He+Xe, Ne+Xe or He+Ne+Xe, to thereby display a picture including characters and graphics. Such a PDP is easy to be made into a thin-film and large-dimension type. Moreover, the PDP provides a very improved picture quality owing to a recent technical development. Particularly, since a three-electrode, alternating current (AC) surface-discharge PDP has wall charges accumulated in the surface thereof upon discharge and protects electrodes from a sputtering generated by the discharge, it has advantages of a low-voltage driving and a long life.
Referring to FIG. 1, a discharge cell of a conventional three-electrode, AC surface-discharge PDP includes a scan/sustain electrode 12Y and a common sustain electrode 12Z provided on an upper substrate 11, and an address electrode 17X provided on a lower substrate 16.
The scan/sustain electrode 12Y and the common sustain electrode 12Z are formed from a transparent electrode material, such as indium-tin-oxide (ITO). Each of the scan/sustain electrode 12 and the common sustain electrode 12Z is provided with a metal bus electrode 13 for reducing a resistance.
An upper dielectric layer 14 and a protective film 15 are disposed on the upper substrate 11 provided with the scan/sustain electrode 12Y and the common sustain electrode 12Z. The protective film 15 prevents a damage of the upper dielectric layer 14 caused by a sputtering during the plasma discharge and improves the emission efficiency of secondary electrons. This protective film 15 is usually made from magnesium oxide (MgO).
A lower dielectric layer 18 and barrier ribs 19 are formed on the lower substrate 18 provided with the address electrode 17X. The surfaces of the lower dielectric layer 18 and the barrier ribs 19 are coated with a fluorescent material layer 20. The address electrode 17X is formed in a direction crossing the scan/sustain electrode 12Y and the common sustain electrode 13Z.
The barrier ribs 19 is formed in a direction parallel to the address electrode 17X to prevent an ultraviolet ray and a visible light generated by the discharge from being leaked to the adjacent discharge cells. The fluorescent material layer 20 is excited by an ultraviolet ray generated upon plasma discharge to produce any one of red, green and blue visible lights. An inactive mixture gas such as He+Xe or Ne+Xe is injected into a discharge space defined between the upper and lower substrate 11 and 16 and the barrier rib 19.
FIG. 2 shows a schematic electrode arrangement of the conventional three-electrode, AC surface-discharge PDP.
Referring to FIG. 2, the conventional three-electrode, AC surface-discharge PDP includes a scan electrode 12Y and a sustain electrode 12Z formed in a parallel to each other, and an address electrode 17X perpendicular to the scan electrode 12Y and the sustain electrode 12Y. A discharge cell 30 is provided at each intersection among the address electrode 17X and a pair of scan electrode 12Y and sustain electrode 12Z. Non-effective display areas 32 and 33 positioned at the outer sides of the upper and lower edges of an effective display area of the PDP are provided with dummy electrodes D. In other words, the dummy electrodes D of the upper non-effective display area 32 are provided at the upper portion of the first scan electrode Y1 positioned at the uppermost portion of the effective display area 31 while the dummy electrodes D of the lower non-effective display area 33 are provided at the lower portion of the nth sustain electrode Z positioned at the lowermost portion of the effective display area 31. The dummy electrodes D play a role to cause a priming discharge so that it can supply priming charged particles to the uppermost line and the lowermost line of the effective display area 31.
In order to realize gray levels of a picture, such a PDP is driven by dividing one frame into various sub-fields having a different discharge frequency. Each sub-field is again divided into a reset period for causing a uniform discharge, an address period for selecting a discharge cell and a sustain period for implementing gray levels depending upon a discharge frequency. For instance, when it is intended to display a picture of 256 gray levels, a frame interval equal to {fraction (1/60)} second (i.e. 16.67 ms) is divided into 8 sub-fields as shown in FIG. 3. Each of the 8 sub-fields is again divided into an address period and a sustain period. Herein, the reset period and the address period of each sub-field are equal every sub-field, whereas the sustain interval and the discharge frequency become different depending upon a brightness weighting value assigned to each sub-field. If a brightness weighting value is increased at a ratio of 2n (wherein n=0, 1, 2, 3, 4, 5, 6 and 7) for each successive sub-field, then each of the sustain period and the discharge frequency is twice increased in proportion to said brightness weighting value 2n whenever the current sub-field is transited into the next sub-field. Gray levels of a picture supplied in one frame interval can be implemented by a combination of the sustain discharge frequency differentiated for each sub-field as mentioned above.
However, the conventional PDP has a problem in that an abnormal discharge is caused by electric charges excessively accumulated at the non-effective display areas 32 and 33 positioned at the outer sides of the uppermost and lowermost portions of the effective display area 31. If such a normal discharge is generated, then a light accompanied by the discharge is diffused into the effective display area 31. Thus, a display quality is deteriorated. Furthermore, a picture fails to be displayed for several seconds and the discharge cell may be damaged in a serious circumstance. The abnormal discharge becomes more serious as a brightness of the PDP goes higher and a resolution of the PDP goes higher.
In order to overcome such an abnormal discharge, Japanese Laid-open Patent Gazette No. Pyung 10-64432 has been suggested a method of removing dielectric materials of the upper and lower edges of the PDP to discharge electric charges accumulated in the non-effective display areas 32 and 33 through the address electrode 17X. Also, Japanese Laid-open Patent Gazette No. Pyung 10-69858 has been suggested a method of providing a normal turn-on area at the upper and lower edges of the PDP to cause a discharge at the normal turn-on area, thereby eliminating electric charges. However, these methods have a problem in that they are effective only when the entire area of the PDP is used as the effective display area, but fails to prevent the abnormal discharge in a case when a portion of the PDP is used as the display area.
Otherwise, Japanese Laid-open Patent Gazette No. Pyung 10-64434 has been suggested a method of mixing conductive particles within a dielectric layer provided with an address electrode to discharge electric charges accumulated in the upper and lower edges of the effective display area by utilizing the dielectric layer. This method has a problem in that it has a difficulty in keeping an electric conductivity of the dielectric layer in the baking process.
Accordingly, it is an object of the present invention to provide a method of driving a plasma display panel and an apparatus thereof that is capable of preventing an abnormal discharge generated at the upper and lower edges of an effective display area of the plasma display panel.
In order to achieve these and other objects of the invention, a method of driving a plasma display panel according to one aspect of the present invention includes the steps of applying a voltage with potential difference enabling discharge to two electrodes opposed to each other with having a space discharge therebetween within an effective display area to select a cell; and applying a constant voltage to a dummy electrode arranged at the outside of the effective display area during an address period for selecting said cell.
The method further includes the step of applying a reset voltage to a scan electrode, which is any one of said two electrodes, prior to selecting said cell to initialize cells of the entire field.
The method further includes the step of synchronizing a voltage having the same polarity as the reset voltage and a lower voltage level than the reset voltage to apply it to an address electrode of said two electrodes.
A method of driving a plasma display panel according to another aspect of the present invention includes the steps of arranging a scan electrode supplied with a scan voltage at the uppermost and lowermost portion of an effective display area and applying a voltage with potential difference enabling discharge to an address electrode crossing the scan electrode and said scan electrode, thereby selecting a cell; and alternately applying a sustain voltage to a sustain electrode making a pair with the scan electrode and said scan electrode to cause a sustain discharge for the selected cell.
In the method, said sustain electrode is arranged successively at at least one portion thereof.
The method further includes the step of arranging a dummy electrode within a non-effective display area being adjacent to the scan electrodes at the uppermost and lowermost portions thereof.
In the method, said voltage applied to the dummy electrode is a negative voltage.
Said address electrodes are divided and said scan electrodes are arranged in such a manner to be adjacent to each other at the divided areas.
A driving apparatus for a plasma display panel according to still another aspect of the present invention includes a driver for applying a voltage with potential difference enabling discharge to two electrodes opposed to each other with having a space discharge therebetween within an effective display area to select a cell between the two electrodes; and a dummy electrode driver for applying a constant voltage to a dummy electrode arranged at the outside of the effective display area during an address period for selecting said cell.
In the driving apparatus, the dummy electrode driver applies a positive voltage to the dummy electrode.
Otherwise, the dummy electrode driver applies a negative voltage to the dummy electrode.
Said driver includes a scan driver for applying a reset voltage, a scan voltage and a sustain voltage to the scan electrode; and an address driver for applying a data voltage synchronized with said scan voltage to the address electrode opposed to the scan electrode with having a discharge space therebetween.
The address driver synchronizes a voltage having the same polarity as said reset voltage and a lower voltage level than said reset voltage with said reset voltage to apply it to the address electrode.
The driving apparatus further includes a sustain driver for applying a sustain voltage to a sustain electrode making a pair with the scan electrode.
A driving apparatus for a plasma display panel according to still another aspect of the present invention includes a first driver for applying a voltage with potential difference enabling discharge to scan electrodes arranged at the uppermost and lowermost portions of an effective display area and an address electrode crossing the scan electrodes to select a cell; and a second driver for alternately applying a sustain voltage to a sustain electrode making a pair with the scan electrode and said scan electrode to cause a sustain discharge for the selected cell.
In the driving apparatus, said sustain electrode is arranged successively at at least one portion thereof.
The driving apparatus further includes a dummy electrode arranged within a non-effective display area being adjacent to the scan electrodes at the uppermost and lowermost portions thereof.
The driving apparatus further includes a dummy driver for applying a negative voltage to the dummy electrode.
Said address electrodes are divided and said scan electrodes are arranged in such a manner to be adjacent to each other at the divided areas.